It is proposed to study quantitatively Tetrodotoxin receptors and membrane-bound enzymes involved in regulation of membrane phosphoproteins in the sarcolemma and sacroplasmic reticulum fractions isolated from striated muscle. Tetrodotoxin receptors will be determined by a binding assay using H3-tin labelled by proton exchange. The activity of the following membrane-associated enzymes will be determined in sarcolemma using P32 or H3 labelled nuceotides (a) protein kinase (b) membrane phosphoproteins (c) phos-phoprotein phosphatase (d) adenylate cyclase (e) quanylate cyclase (f) phosphodiesterase. The levels of TTX-receptors and their binding properties as well as all the above enzyme activities will be compared in membranes from normal, denervated and murine dystrophic muscles. The influence of inhibitors of protein synthesis (Actinomycin D. Cycloheximide) and antimitotic drugs (Colchicine, Vinblastine) on denervation induced changes in the above enzyme systems will also be evaluated. The principal aim of the proposed research is to identify and quantitate specific membrane proteins of muscles that are regulated by the motorneuron and are correlated with altered membrane function.